Mount Etna
Mount Etna (also known locally as
Mongibeddu in
Sicilian and
Mongibello in
Italian) is an active
volcano on the east coast of
Sicily, close to
Messina and
Catania. It is the largest active volcano in
Europe, currently standing about 3,350 m (10,991 ft) [
1] high, though it should be noted that this varies with summit eruptions; the mountain is 21.6 m (71 ft) lower now than it was in
1865. It is the highest mountain in Italy south of the
Alps. Etna covers an area of 1190 km² (460 square miles) with a basal circumference of 140 km. This makes it by far the largest of the three
active volcanoes in Italy, being nearly three times the height of the next largest,
Mount Vesuvius.
It is one of the most active volcanoes in the world and is in an almost constant state of eruption. Although it can occasionally be very destructive, it is not generally regarded as being particularly dangerous, and thousands of people live on its slopes and in the surrounding areas. The fertile volcanic soils support extensive
agriculture, with
vineyards and
orchards spread across the lower slopes of the mountain and the broad Plain of Catania to the south.
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A crater near the Torre del Filosofo, about 450 metres below Etna's summit |
Etna was known in
Roman times as
Aetna, a name thought to have derived either from the
Greek word
aitho ("to burn") or the
Phoenician word
attano. The
Arabs called the mountain
Gibel Utlamat ("the mountain of fire"); this name was later corrupted into
Mons Gibel (translating from its Roman and Arab parts as 'Mountain Mountain', since such repetition in Sicilian denotes largeness or greatness) and subsequently Etna's current local name
Mongibeddu.
The mountain's regular and often dramatic eruptions made it a major subject of interest for
Classical mythologists and their later successors, who sought to explain its behaviour in terms of the various gods and giants of Roman and Greek legend.
Aeolus, the king of the winds, was said to have imprisoned the winds in caves below Etna. The giant
Typhon was confined under Etna, according to the poet
Aeschylus, and was the cause of the mountain's eruptions. Another giant,
Enceladus, rebelled against the gods, was killed and was buried under Etna.
Vulcan, the god of fire and the forge, was said to have had his forge under Etna and drove the fire-demon
Adranus out from the mountain, while the
Cyclopes maintained a smithy there where they fashioned lightning bolts for
Zeus to use as a weapon. The Greek underworld,
Tartarus, was supposed to be situated beneath Etna.
Empedocles, a major pre-Socratic philosopher and Greek statesman of the
5th century BC, was said to have met his death in the volcano's crater. Etna supposedly erupted in sympathy with the martyrdom of
Saint Agatha in
251 CE, prompting
Christians thereafter to invoke her name against fire and lightning.
Etna is an isolated peak about 29 km (18 miles) from
Catania which dominates the eastern side of Sicily. Its shape is that of a truncated cone with a ragged top, which is actually a complex of large
volcanic cones hosting four summit craters. Around 260 smaller craters, formed by
flank eruptions, occupy the slopes. On the southeastern side of Etna lies an immense gorge, the
Valle del Bove, which is between 600-1200 m (2000-4000 ft) deep and over 5 km (3 miles) wide. Many of Etna's subsidiary craters reside within this cleft, which is thought to have been created around 3,500 years ago by the collapse of an ancient
caldera. The height of the mountain varies with its eruptions; until
1911, there was only one large cone and crater at the summit, but subsequent eruptions have created new craters and cones.
The slopes of Etna form three distinct zones. The lower zone, extending up to about 1200 m (4000 ft) are densely populated and planted with
vineyards,
citrus fruits, and groves of
olives,
figs and
almonds. The middle zone (up to about 2100 m/6900 ft) is heavily wooded, mostly with
pine and
chestnut trees. At the top of the mountain is a volcanic wasteland, dominated by old lava flows, screes and volcanic ash. Few plants grow there and it is covered by snow for much of the year.
Etna is an extremely complex volcano, presenting considerable difficulties in classification. It has features of both a
shield volcano and a
stratovolcano, and displays behaviour typical of both
plinian and
strombolian volcanoes. It stands at the
convergent boundary where the
African Plate is being
subducted beneath the
Eurasian Plate, deforming the latter and forcing plumes of
magma upwards into weak points in the crust such as under Etna. It is perhaps most accurate to describe Etna as being a mixture of overlapping shield and strato volcanoes partially destroyed by repeated collapses and partly buried under subsequent volcanic edifices.
 |
House destroyed by lava on the slopes of Etna. |
Volcanic activity at Etna began about half a million years ago, with eruptions occurring beneath the sea off the then coastline of Sicily. 300,000 years ago, volcanism began occurring to the southwest of the present-day summit, before activity moved towards the present centre 170,000 years ago. Eruptions at this time built up the first major volcanic edifice, forming a stratovolcano in alternating explosive and effusive eruptions. The growth of the mountain was occasionally interrupted by major eruptions leading to the collapse of the summit to form
calderas.
From about 35,000 to 15,000 years ago, Etna experienced some highly explosive eruptions, generating large
pyroclastic flows which left extensive
ignimbrite deposits. Ash from these eruptions has been found as far away as
Rome, 800 km to the north.
About 3,500 years ago, the eastern flank of the mountain experienced a catastrophic collapse, generating an enormous landslide in an event similar to that seen at
Mount St. Helens in 1980. The eruption which is thought to have caused this collapse was recorded by
Diodore of Sicily, the first known record of an eruption at Etna. The landslide left a large depression in the side of the volcano, known as 'Valle del Bove' (Valley of the Oxen). The steep walls of the Valle have suffered subsequent collapse on numerous occasions. The
strata exposed in the valley walls provide an important and easily accessible record of Etna's eruptive history.
The most recent collapse event at the summit of Etna is thought to have occurred about 2,000 years ago, forming what is known as the Piano Caldera. This caldera has been almost entirely filled by subsequent lava eruptions, but is still visible as a distinct break in the slope of the mountain near the base of the present-day summit cone.
The Roman poet
Virgil gave what was probably a first-hand description of an eruption in the
Aeneid:
In
396 BC, an eruption of Etna is said to have thwarted the
Carthaginians in their attempt to advance on
Syracuse during the
First Sicilian War.
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Contemporary drawing showing the devastating effects of Etna's 1669 eruption |
Over the last 2000 years, activity at Etna has been generally effusive, with occasional explosive eruptions from the summit. Its most destructive eruption during this time occurred in March 1669, when an estimated 830,000,000 m³ of lava was ejected. The eruption was preceded by two months of increasingly powerful
earthquakes centred on the southern slopes of the mountain, which eventually encouraged most villagers there to abandon their homes. On
11 March, a 9 km-long
fissure opened up on the southern flank of the mountain, stretching from an elevation of 2800 m down to 1200 m. Activity steadily migrated downslope, and the largest vent eventually opened near the town of
Nicolosi. The
cinder cone built up at the erupting vent became known as
Monti Rossi (red hills), and is still a prominent landmark today.
Nicolosi was quickly destroyed by lava flows, and two nearby villages were also destroyed during the eruption's first day. The eruption was extremely voluminous, and a further four villages were destroyed in the following three days as the lava flowed south. In late March two larger towns were destroyed, and the lava reached the outskirts of Catania in early April.
At first, lava piled up against the
city walls, which were strong enough to withstand the pressure of the flow. However, while the city was temporarily protected, lava flowed into its
harbour and filled it in. On
30 April, lava flowed over the top of the city walls, which then gave way. Catanians built walls across major roads to halt the flow of the lava, which were fairly effective but did not prevent the destruction of the western side of the city.
During the eruption, Catania residents also attempted to divert the flows much further upstream. According to a possibly apocryphal tale, their efforts were met with armed resistance from the citizens of a town which would have been threatened by the diverted flow [
2]. Whether this event really occurred or not, a law was subsequently passed to forbid the artificial diversion of lava flows. This law was only repealed in 1983.
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Etna's 2002 eruption, photographed from the ISS |
Another very large lava flow from an eruption in
1928 led to the first destruction of a town since the 1669 eruption. In this case, the town of
Mascali was destroyed in just two days, with the lava destroying every building. The event was used by
Mussolini's
Fascist regime for
propaganda purposes, with the evacuation, aid and rebuilding operations being presented as models of fascist planning. Mascali was rebuilt on a new site, and its church contains the Italian fascist symbol of the torch, placed above the statue of
Christ.
Other major twentieth century eruptions occurred in
1949,
1971,
1983,
1992, and
2000. The 1992 eruption saw the town of
Zafferana threatened by a lava flow, but successful diversion efforts saved the town with the loss of only one building a few hundred metres outside it.
In
2002-
2003, the biggest series of eruptions for many years threw up a huge column of ash that could easily be seen from space and fell as far away as
Libya, on the far side of the
Mediterranean Sea. Seismic activity in this eruption caused the eastern flanks of the volcano to slip by up to two metres, and many houses on the flanks of the volcano experienced structural damage. The eruption also completely destroyed the Rifugio Sapienza, on the southern flank of the volcano. The Rifugio was the site of a
cable car station which had previously been destroyed in the
1983 eruption; both have now been rebuilt. The most recent eruption was in July 2006.
*
Mount Etna Live Webcam*
Italy's Volcanoes: The Cradle of Volcanology, with detailed information of Italy's volcanoes, including Etna*
Stromboli Online, with info on Etna as well as excellent photo galleries and video clips of Etna's past eruptions including those of the 1990s and the 2000s*
Volcano Etna, with news on Etna as well as photo galleries and video clips of Etna's past eruptions including those of the 2001, 2002 and 2004
